A. Field of the Invention
The present invention relates to a furnace construction, and more particularly to a roof unit for placement on top of refractory furnace walls. Specifically, the present invention pertains to a novel truss-panel roof assemblage formed as a unit which may be readily situated on or removed from a supported position on top of refractory wall panels in a furnace.
In furnace constructions it is often desirable to provide upright refractory panel walls which are spaced rather widely apart. Consequently, a refractory roof structure which spans the distance between the walls without the need for interior upright supports is preferable. Refractory walls and roof panels may include a rectangular iron frame over which an expanse of expanded metal grate has been secured. Attached to such a grate and distributed over a major portion thereof are anchors. A thick layer of cementitious refractory material is formed over the grate and around the anchors. While such a construction provides for an efficient insulative wall or roof panel, it is not satisfactory from a structural standpoint to span relatively long distances. Specifically, such a panel has little resistance to bending moments over large spans and hence additional structural support is required to adequately maintain a refractory roof panel across refractory wall panels.
Additionally, if substantial temperatures are created within a furnace, refractory wall panels will tend to swell and distort which can result in damage to a refractory roof panel structure. If the refractory roof panel is supported, i.e., as by being suspended from a truss or the like, additional resistance to bending moments will be imparted to the roof panel. Furthermore, it is desirable to have a roof panel structure which can be readily lifted onto and from refractory wall panels if it is desired to replace a damaged roof panel or if it is desired to enlarge, tear down, etc. a furnace construction.
B. Description of the Prior Art
Furnace constructions utilizing refractory wall and roof panels are well known in the art, and several proposals have been set forth directed to strengthening a refractory roof panel structure. One example is described in U.S. Pat. No. 3,670,469 wherein a furnace construction utilizes walls which hang on an exterior steel supporting frame. The wall panels are precast and hang from their upper ends from steel I-beam columns which are in turn secured to a concrete foundation. The roof of the furnace comprises apertured refractory blocks which are hung on horizontal rods, the rods being suspended by vertical hanger rods from the lower flanges of an upper I-beam. It is apparent that the furnace structure of this patent requires additional outer I-beam steel framework for providing structural integrity to the wall panels and roof panels.
Another example of refractory blocks forming a roof of a furnace is disclosed in U.S. Pat. No. 1,339,615. Here, a flat arch of refractory material is extending between and supported on side walls of a furnace. Tie rods extend through openings in the arch and serve to provide resistance to bending. In order to accommodate the tie rod, the arch must be constructed of arch-tiles having openings through which the tie rods extend.
A suspended arch for furnaces is described in U.S. Pat. No. 1,921,107. This patent sets forth a furnace construction in which a plurality of tiles are suspended by means of a plurality of suspension bars which have their opposite ends placed on top of side walls of refractory brick material. Such a construction contemplates that each tile be configured with an upsidedown T-slot for enabling the tiles to be slidably disposed upon T-shaped hangers.
A last prior art patent to be considered is U.S. Pat. No. 1,751,675 which describes a removable furnace roof in which units made up of refractory tile are suspended from cross beams so as to be freely adjustable relative to each other under expansion and contraction in any horizontal direction. The cross beams are seated at their opposite ends upon brick-like elements 11 which in turn are placed upon the top of upright vertical walls of a furnace. This patent apparently has as its main object the adjustability relative to each other of refractory roof elements or tiles.